1. Field of the Invention
This invention relates to a three-piece solid golf ball of the three layer structure consisting of a solid core, an intermediate layer, and a cover. The invention provides a golf ball having the desirable properties of spin, feel, control and distance.
2. Prior Art
Golf balls which have been commercially available for decades include solid golf balls having a solid core enclosed with a cover of synthetic rubber and wound golf balls having a wound core (obtained by winding thread rubber around a liquid center) enclosed with a cover of natural rubber, typically balata rubber and synthetic rubber. While solid golf balls having a cover of synthetic rubber featuring added distance and durability enjoy widespread use, many professional golfers still favor a wound golf ball having a cover of balata rubber, which is simply referred to as wound balata ball, hereinafter.
The reason is that the wound balata ball has superior hitting feel and spin control to the remaining golf balls. Although professional golfers seek a golf ball offering a longer flight distance, they seldom consider distance as the first condition for ball selection, but place more stress on hitting feel and spin control.
In order to produce a golf ball which not only complies with such professional golfers' needs, but is also suited for ordinary golfers' play, various proposals have been made on solid golf balls so as to impart the desirable properties of distance, feel and spin control. For example, JP-B 4110/1993 and JP-A 319830/1994 disclose a two-piece solid golf ball which has a good feel and is improved in control by adjusting spin property. Also proposed were three-piece solid golf balls of the three layer structure consisting of a solid core, an intermediate layer, and a cover as disclosed in JP-A 92372/1983, 24085/1995, 343718/1994, 194735/1995, 194736/1995 and 239068/1997. There were proposed many three-piece solid golf balls which are designed to improve feel and control.
Despite such improvements, many players still use the wound balata ball because the solid golf balls proposed thus far have not reached the feel and spin control levels above which these players are satisfied. In particular, spin control is one of the most important factors for the performance of golf balls. It is thus strongly desired to improve the spin control of solid golf balls without detracting from the remaining properties of distance and feel.
The spin property of solid golf balls can be improved to some extent by making the cover soft. The soft cover, however, lowers the resiliency of the ball, resulting in a reduced flight distance. That is, the superior flight performance characteristic of solid golf balls is lost.
In general, golf clubs used for distance shots such as a driver and long irons have a small loft angle whereas golf clubs used for aiming at the pin or a target such as short irons have a large loft angle and are designed to stop the ball at the desired position rather than distance. When a golf ball is hit with a golf club, the ball receives both a force acting perpendicular to the club face and a force acting parallel to the club face depending on the loft angle. The perpendicular force contributes to deriving resiliency from the ball whereas the parallel force contributes to spinning the ball. On shots with driver and long iron clubs having a small loft angle, the perpendicular force becomes greater while the parallel force is relatively weak. These clubs are designed for distance by imparting an appropriately suppressed spin rate, a relatively low trajectory, and greater resiliency. Inversely, on shots with short iron clubs having a large loft angle, the parallel force becomes greater while the perpendicular force is relatively weak. These clubs are designed to give a greater spin to the ball rather than distance.
Therefore, simply increasing a spin rate is not sufficient. It is desired that upon shots with driver and long iron clubs, a flight distance is ensured by an appropriately suppressed spin rate which restrains flight distance shortage and wind influence which are otherwise caused by the lofting of the ball by spin (to follow a higher trajectory than necessary). Upon shots with short iron clubs for aiming at the target, the ease of control is ensured by a sufficient spin rate leading to a relatively high trajectory and a reduced run or roll after the ball lands. Sufficient in-flight retention of the spin rate given by a strike is also important for the flight distance to be increased and for the spin control to be effective.
Another problem arises upon putting. Unlike ordinary shots to drive the ball into flight, putting rolls the ball on the green so that the ball may readily change its path by angulation on the green. Since putting directly aims the hole, successful putting improves the score and vice versa. What is desired in this regard is a golf ball which rolls well and goes straight upon putting without being affected by subtle angulation.